A conventional shorts for male (referred to as “shorts” hereinafter) is as shown in FIGS. 19-23 for example. FIGS. 19 and 20 show a front view and a rear view of the conventional shorts S′, respectively.
In the front face of the shorts S′, there is provided a front opening portion 100′ capable of forming an opening 101. At this front opening 100′, there are disposed a pair of cloth members 1a, 2a, overlapped one on the other (hatched portion in FIG. 21), and edge portions 2X, 2Y of the respective cloth members 1a, 2a being not sewn with the other cloth member. For urination, approximate mid points 2E, 2F of the respective edge portions 2X, 2Y are pulled away from each other to form the opening 101 (FIGS. 21, 22). And, through this opening 101 formed by deforming the cloth members 1a, 2a, the penis P can be inserted.
In the cloth members 1a, its portion upwardly of an upper end 2A of the edge portion 2X and a further portion downwardly of a lower end 2B of the same are sewn and joined with the other cloth member 2a. On the other hand, in the cloth members 2a, its portion upwardly of an upper end 2C of the edge portion 2Y and a further portion downwardly of a lower end 2D of the same are sewn and joined with the other cloth member 1a. The four points formed by the upper ends 2A, 2C and the lower ends 2B, 2D are set on front crotch cut if, 2f, so that the front opening portion 100′ is formed substantially quadrangle by the overlapping of the two cloth members 1a, 2a. 
As shown in FIG. 22, in association with the deformation of the cloth members 1a, 2a in the course of the formation of the opening 101, the end portions of the edge portion 2X are displaced to positions of an upper end 2A′ and a lower end 2B′ and the ends of the edge portion 2Y are displaced to positions of an upper end 2C′ and a lower end 2D′. As described above, the deformation of the front opening portion 100′ takes place over the entire shorts S′ as shown by e.g. the displacement of a waist position W to a position W.
The front opening portion 100′ comprised of the quadrangle interconnecting the four points of the upper ends 2A, 2C and the lower ends 2B, 2D has a significant area of overlapping between the two cloth members 1a, 2a and this portion 100′ is formed rather flat (see FIG. 23). Therefore, in order to form the opening 101, the respective edge portions 2X, 2Y need to be displaced by large amounts, so this opening operation is troublesome. For this reason, with the conventional shorts S′, in an attempt to minimize the opening movement, the edge portions 2X, 2Y are curved toward the center of the shorts S′, thereby reducing the overlapping area between the cloth members 1a, 2a. 
Incidentally, as the above-described prior art is of general technical contents, no specific prior-art document is cited.